RFR: 8298126: Print statistics for objects in CDS archive heap [v3]

[Ioi Lam]

> For diagnostic purposes, it's useful to print out statistics of the objects in the CDS archive heap. For example, this shows the number of objects with a distribution of different sizes.
> 
> 
> [6.772s][info][cds,heap]        0 objects are <= 8      bytes (total        0 bytes, avg      0.0 bytes)
> [6.772s][info][cds,heap]     1205 objects are <= 16     bytes (total    19280 bytes, avg     16.0 bytes)
> [6.772s][info][cds,heap]    15717 objects are <= 32     bytes (total   411024 bytes, avg     26.2 bytes)
> [6.772s][info][cds,heap]     4127 objects are <= 64     bytes (total   198080 bytes, avg     48.0 bytes)
> [6.772s][info][cds,heap]     2380 objects are <= 128    bytes (total   243016 bytes, avg    102.1 bytes)
> [6.772s][info][cds,heap]      293 objects are <= 256    bytes (total    47920 bytes, avg    163.5 bytes)
> [6.772s][info][cds,heap]       51 objects are <= 512    bytes (total    17112 bytes, avg    335.5 bytes)
> [6.772s][info][cds,heap]       18 objects are <= 1024   bytes (total    14480 bytes, avg    804.4 bytes)
> [6.772s][info][cds,heap]       11 objects are <= 2048   bytes (total    13440 bytes, avg   1221.8 bytes)
> [6.772s][info][cds,heap]        3 objects are <= 4096   bytes (total     9808 bytes, avg   3269.3 bytes)
> [6.772s][info][cds,heap]        3 objects are <= 8192   bytes (total    12840 bytes, avg   4280.0 bytes)
> [6.772s][info][cds,heap]        4 objects are <= 16384  bytes (total    37240 bytes, avg   9310.0 bytes)
> [6.772s][info][cds,heap]        0 objects are <= 32768  bytes (total        0 bytes, avg      0.0 bytes)
> [6.772s][info][cds,heap]        0 objects are <= 65536  bytes (total        0 bytes, avg      0.0 bytes)
> [6.772s][info][cds,heap]        0 objects are <= 131072 bytes (total        0 bytes, avg      0.0 bytes)
> [6.772s][info][cds,heap]        0 objects are <= 262144 bytes (total        0 bytes, avg      0.0 bytes)
> [6.772s][info][cds,heap]        0 huge  objects               (total        0 bytes, avg      0.0 bytes)
> [6.772s][info][cds,heap]    23812 total objects               (total  1024240 bytes, avg     43.0 bytes)
> 
> 
> These stats are useful when implement large changes in the CDS heap archiving code. For example, [JDK-8296344](https://bugs.openjdk.org/browse/JDK-8296344) significantly changes how the objects are copied into the archive. We can use these stats to verify that the exact same objects are copied.

Ioi Lam has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - Merge branch 'master' into 8298126-print-archive-heap-stats
 - @ashu-mehra comments
 - 8298126: Print statistics for objects in CDS archive heap

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/11520/files
  - new: https://git.openjdk.org/jdk/pull/11520/files/9c48fd09..a6c02c20

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11520&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11520&range=01-02

  Stats: 22255 lines in 565 files changed: 16208 ins; 4064 del; 1983 mod
  Patch: https://git.openjdk.org/jdk/pull/11520.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11520/head:pull/11520

PR: https://git.openjdk.org/jdk/pull/11520